.clouds {
    z-index: 0;
    position: absolute;
    top: 0; bottom: 0; right: 0;
    width: 10000px; height: 100%;
    background: rgba(0, 0, 0, 0.75) url('../images/clouds.png') repeat;
    background-size: contain;
    animation: move-background 150s linear infinite;-moz-animation: move-background 150s linear infinite;-ms-animation: move-background 150s linear infinite;-o-animation: move-background 150s linear infinite;-webkit-animation: move-background 150s linear infinite;
}

@keyframes move-background {
    from { -webkit-transform: translate3d(0px, 0px, 0px); }
    to { -webkit-transform: translate3d(1000px, 0px, 0px); }
} @-webkit-keyframes move-background {
    from {-webkit-transform: translate3d(0px, 0px, 0px);}
    to {-webkit-transform: translate3d(1000px, 0px, 0px);}
} @-moz-keyframes move-background {
    from { -webkit-transform: translate3d(0px, 0px, 0px); }
    to { -webkit-transform: translate3d(1000px, 0px, 0px); }
}